Survival of Africanized Apis mellifera after intoxication with thiamethoxam using different routes and doses

Insecticides belonging the class of neonicotinoids have been related as one of the responsible for the decline of managed and wild bees around the world. Among them, thiamethoxam is one of the most employed to pest control and its usage takes as advantage the properties to be systemic. However, as this insecticide could contaminate pollen and nectar, great concern has been raised about the risk against Apis mellifera L., 1758 either at lethal and sublethal levels. Therefore, this study has as goal the assessment of Africanized honey bee survival after the intoxication with thiamethoxam using different routes (acute and chronic ingestions, dermal by topical application and the contact with treated area) and doses (control, LD50, 1/10 of LD50 and 1/20 of LD50). Our results show that the survivals of honey bees were impaired after the intoxication with thiamethoxam even at sublethal dose. After the ingestion of the LD50 (11.13 ng/honey bee), we observe a reduction of lifespan in average of 47 and 80% for the acute and chronic ways. When in sublethal doses, the reduction of survivorship was in average of 6% for ingestion and for the contact with treated areas (Petri dish) and of 58% for topical application on thorax. From our outcomes is evident the risk of thiamethoxam for honey bees in laboratory condition (independent of routes and doses), but further investigations should be developed to complementary the risk assessment and specially using high tier level, as for example the studies of semi-field and open field.

Key-words: Honey bee, pesticide, survivorship